The demand for better controllability and efficiency in work machine operations have lead to an increasing use of load sensing hydraulic systems. Compared to conventional hydraulic systems, load sensing hydraulic systems containing variable displacement pumps are more efficient since both the pump flow and the pump pressure are continuously matched to the actual load. Load sensing valve system configurations can be derived from both conventional closed-center and open-center type valves and a wide variety of different system configurations are being used. Different valve configuration yield different operational characteristics. Regardless of the particular valve configuration being utilized, it is always difficult to produce a load signal which is indicative of the actual load and which can be communicated to the pump controller without utilizing special load sensing valve mechanisms. It is also difficult to duplicate a true high pressure load sensing signal for communication with the pump controller without having a high pressure source associated therewith.
It is therefore desirable to provide a load sensing signal to the pump controller of a variable displacement hydraulic pump without utilizing special porting or other special valve means to mechanically control such signal, and without utilizing structure such as pressure compensating valves within the main control valve network to accomplish this task. It is also desirable to provide a mechanism for reducing or scaling down a high pressure load signal to a desired lower pressure load signal which will be representative of the actual load being experienced by the hydraulic system.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.